Circuit breakers are well known in the art, and are designed to trip in response to an electrical interruption event caused by an overload, short circuit, or thermal runaway condition, thereby opening the circuit to which the circuit breaker is connected and reducing the possibility of damage to the conductor wires or the loads connected to the circuit breaker. During the electrical interruption event, hot explosive gasses are generated and are released away from an interrupter assembly of the circuit breaker as the internal contacts inside the circuit breaker separate. In addition, during the electrical interruption event, molten metal debris and carbon are produced, spraying outward in the direction of the gas, and can accumulate inside the circuit breaker. The accumulation of this carbon and molten metal debris can eventually produce undesirable ground strikes or cross-phasing caused by dielectric breakdowns, reducing the electrical performance of the circuit breaker. In addition, the sudden explosion of gas causes a sudden increase in pressure in the surrounding area of the explosion.
As the overall size of the circuit breaker is reduced, vents have been introduced to vent these potentially destructive gasses and debris away from internal components of the circuit breaker. The contacts are housed inside an interrupter assembly which has an opening through which the gasses pass during an electrical interruption event. The forces caused by the pressure buildup inside the circuit breaker can cause undesirable internal or external physical damage to the housing and components of the circuit breaker. In addition, the pollution caused by a buildup of molten metal debris and carbon inside the circuit breaker can eventually cause ground strikes or dielectric breakdowns between the phases of current in the circuit breaker.
In order to meet present UL requirements, the integrity of the circuit breaker case must be maintained. Therefore, pressure caused by an electrical interruption event must be controlled and suppressed. Pressure blowouts that cause damage to a circuit breaker will fail present UL requirements and will fail customer expectations. A damaged circuit breaker may also present a safety hazard as the blowout may expose internal components of the circuit breaker to the operator or may cause internal shorting or melting of circuit-breaker components not designed for high current loads.
What is needed, therefore, is an arrangement that reduces pressure that builds up inside a circuit breaker during an electrical interruption event by employing an efficient venting means to direct gas toward vents while maintaining the physical integrity of the circuit breaker and reducing cross-phasing effects caused by accumulation of carbon and molten metal debris expelled during an electrical interruption event. The present invention is directed to satisfying this and other needs, as more fully described in the detailed description and illustrated in the accompanying drawings.